On August 6 and 9, 1945, the United States dropped two atomic bombs on Japan, ending World War II and inaugurating the nuclear age. This chapter examines the US decision to use atomic weapons on Japan and the origins of a nuclear taboo in the period up to 1950. In 1945, the atomic bomb was widely accepted as a legitimate weapon of war. Most politicians and generals regarded it as completely natural to use the atomic weapons they had at hand to end the war against Japan as speedily as possible. Yet by the time of the Korean War, five years later, significant inhibitions on the use of atomic weapons were already evident, and these cannot be accounted for by deterrence.

The origins of the taboo lay especially in a set of policy precedents and categories established by President Truman and the United Nations which marked out nuclear weapons as different from other weapons. These efforts were propelled by fears of the destructive power of the new weapon, the shock and horror of the Japan bombings, and the moral qualms of key leaders, especially Truman.

With the end of the Cold War, nuclear proliferation replaced superpower conflict as the major threat to the tradition of nuclear non-use. The actual and potential spread of nuclear weapons to new states, mostly in the developing world and in areas of regional tensions, combined with the diminished threat of superpower nuclear use, altered the context which had shaped the nuclear taboo since 1945. With the disappearance of the East–West conflict, the politics of nuclear non-use now became predominantly a North–South issue.

This chapter analyzes nuclear trends since the Gulf War, and the links between taboo and nuclear non-proliferation regime.

Of all cases of Cold War conflict in which the United States could have used nuclear weapons, the Vietnam War provides one of the strongest “tests” of a nuclear taboo. In Vietnam, the United States chose to lose a humiliating and destructive war against a small, non-nuclear adversary while all its nuclear weapons remained on the shelf. During the ten-year military commitment to South Vietnam in the 1960s and 1970s, the United States sustained large losses in men, money, and materiel at tremendous political cost. US officials repeatedly declared that the United States could not tolerate the loss of Southeast Asia to Communism, and that the war was vital for US interests, prestige, and security.

As the war escalated, the United States was willing to maintain policies of great destructiveness. Operation Rolling Thunder, begun in March 1965, continued for three years and dropped more bombs on Vietnam than were dropped on all of Europe in World War II. Starting in 1969, B-52 raids demolished vast areas in North and South Vietnam, Cambodia, and Laos. US forces employed herbicides and defoliants to obliterate croplands and forests, dropped flame throwers and napalm, and eventually mined Haiphong harbor. It is estimated that some 3.6 million Vietnamese in both North and South, were killed in the conflict, and 58,000 Americans.

Iraq's surprise invasion of Kuwait in August 1990 raised once again the issue of use of nuclear weapons. Iraq's extensive conventional capabilities, past history of chemical-arms use, known interest in acquiring nuclear weapons, and revisionist ambitions, made it a textbook case of a post-Cold War Third World adversary. The United States ultimately deployed 500,000 troops to Kuwait in the fastest, farthest, and largest military deployment in the country's history, fought a 35-day air war and a 4-day ground war to defeat Iraq. US leaders ruled out using nuclear weapons even though Iraq was a non-nuclear adversary.

It might be argued that the Gulf War does not offer a good test of the nuclear taboo because the kind of dire circumstances that would call up consideration of a nuclear option never really emerged for the United States and its coalition allies. Nevertheless, this case is significant. It represents the first major conflict of the post-Cold War world, when the threat of nuclear confrontation with the Soviet Union had largely evaporated. At the time, Iraq wielded the world's fourth largest conventional army.

Starting in the early 1960s, the nuclear taboo, which had heretofore been tentative, began to become institutionalized in arms control agreements and internalized by US leaders. The non-use of nuclear weapons in the Vietnam War helped to further reinforce the taboo and the tradition of non-use. Use of nuclear weapons there, however, in addition to being inconsistent with American political goals in the war, would also have undercut a central US foreign policy endeavor emerging in the 1960s: the renewed and more serious efforts, especially after the 1962 Cuban missile crisis, to pursue nuclear arms control and stabilize the arms race.

As noted in Chapter 3, antinuclear-weaponism had been institutionalized in the UN disarmament machinery from an early date. Now the nuclear taboo began to become institutionalized more broadly in multilateral and bilateral arms control agreements and within the US government itself. This institutionalization was often implicit (as in the 1972 Anti-ballistic Missile Treaty, discussed below), but in some cases was quite explicit (as in nuclear non-use commitments associated with nuclear-weapons-free zones). The shift toward institutionalization was made possible by widespread acceptance by US leaders of the view that nuclear weapons should be for deterrence, not use.

As late as 1958 Lt.-Gen. James Gavin, a principal promoter in the US military of the development of tactical nuclear weapons, could still confidently assert that they would become just another weapon in the US arsenal because of their clear military utility and cost-benefit advantages. Indeed, during the 1950s, numerous US leaders fully expected that nuclear weapons would eventually become “just another weapon.” Secretary of State John Foster Dulles accepted the “ultimate inevitability” that tactical nuclear weapons would gain “conventional” status. Admiral Arthur Radford, chairman of the Joint Chiefs of Staff under President Dwight Eisenhower, predicted in 1956 that the use of nuclear weapons “would become accepted throughout the world just as soon as people could lay their hands upon them.” Instead, the developing public opprobrium against such weapons continued to grow. To the distress of Eisenhower and many of his advisors, it came to apply to all nuclear weapons, not just to large bombs or to certain types or uses of nuclear weapons.

In Chapter 4 I showed how, already during the Korean War, a tentative taboo on nuclear weapons constrained US leaders from a casual resort to their use, even though such weapons might have been militarily useful in the war.

More than sixty years have passed since the American use of atomic bombs on Hiroshima and Nagasaki, the only use of nuclear weapons in warfare. The non-use of nuclear weapons since then remains the single most important phenomenon of the nuclear age. Yet we lack a full understanding of how this situation arose and is maintained, and of its prospects for the future. As military historians have noted, it is rare for a weapon found useful on one occasion to remain unused in the next. Such an outcome was not inevitable. At the height of the nuclear arms race in the 1980s, nearly 70,000 nuclear weapons existed in the world's nuclear arsenals. In addition, an extensive array of military plans and organizations, national policies, public commitments, and alliances all contemplated the employment of such weapons. Many reasonable observers expected that nuclear weapons would be used at some point during the Cold War. It was thus by no means inevitable that, after their use against Japan in August 1945, a “tradition” of non-use would arise.

The dominant explanation for why nuclear weapons have remained unused since 1945 is deterrence, an explanation routinely mentioned in almost any text on the role of nuclear weapons during the Cold War. In this chapter I critique this explanation, along with several other competing explanations for the non-use of nuclear weapons, on both theoretical and empirical grounds. I then introduce the taboo argument and outline the role of a nuclear taboo in inhibiting the use of nuclear weapons by the United States since 1945. I lay out a framework for evaluating the influence of the taboo in terms of three effects of norms and three pathways by which norms have effects. I then review the leading theories of norm formation and offer a model of how the nuclear taboo developed.

It is often noted that studying non-events – such as the non-use of nuclear weapons – poses special challenges for analysis. It would seem especially difficult to identify the causes of something that did not happen. Yet the study of important non-occurrences is central to the study of international politics (and social life in general, for that matter). We study why revolutions did not occur in some countries, why the debt crisis of the 1980s did not bring the international monetary system down, why the Cold War did not become a hot war, or why ethnic conflict does not break out in some regions.

This book had its origins in what seemed to me a disconnect between how ordinary people, including many policymakers, have viewed nuclear weapons and how academic deterrence theory has approached the analysis of such weapons. In college I had been involved in the nuclear freeze movement, aimed at halting the US–Soviet nuclear arms race. Most people in this movement shared a deep sense of revulsion at the tremendous destructive power of nuclear weapons, and held their use to be immoral and irrational.

Later, in graduate school, I studied academic deterrence theory. It focused on the cold, hard calculus of making credible threats of massive destruction. These game-theoretic analyses, I found, had little to say about issues of revulsion and morality. Further, when I studied how we managed to avoid nuclear war during the Cold War, it increasingly appeared to me that deterrence was not the whole story. Deterrence could not explain, for example, why nuclear weapons had not been used when the other side did not possess such weapons. I found it hard to avoid a sense that a powerful revulsion associated with nuclear weapons had played a role in inhibiting their use.

If indeed a nuclear taboo exists, how do we know, and how exactly did this taboo emerge? How has it influenced leaders? I decided to find out. This book is the result.

Only two years after the Berlin crisis, and five years after the end of the war against Japan, US leaders were again forced to confront the issue of use of nuclear weapons. As the first case of overt aggression against a US ally in the postwar period, the North Korean attack upon South Korea in June 1950 could well have provided an occasion for use of atomic weapons by the United States. The Korean War was the most serious crisis of the first postwar decade. Like the war against Japan, the Korean War was fought against illiberal Asian aggressors. In December 1950, with Chinese troops routing US–UN forces, the Cold War was in full swing. In the eyes of some observers, the United States faced “the greatest danger in our history” including the “destruction of Western civilization and of our American way of life.”

The Korean War was also the first war since World War II in which a country possessing atomic weapons had engaged in combat. Given that nuclear weapons had become the centerpiece of US defense strategy after 1948, there was every reason to expect that US leaders would use their new weapon to defend or advance American interests in any Cold War conflict. Indeed, numerous American military leaders fully expected that this would be the case.